When a key player goes down with a significant injury it often prompts speculation about whether or not a team will seek to make a trade to compensate for the loss. The Red Sox nearly flipped the script on that scenario in the wee morning hours on Saturday. At roughly 2 a.m. Saturday, the news broke that Boston had acquired Diamondbacks closer Brad Ziegler for a pair of Sally Leaguers, but it wasn’t until close to mid-day that the team announced that incumbent closer Craig Kimbrel would miss three to six weeks following surgery to repair a medial meniscus tear in his left knee.

Fortuitous isn’t quite the right word to describe that confluence of events. The Red Sox had been in talks with Arizona over Ziegler for several days before Kimbrel hurt his knee shagging flies in batting practice prior to Boston’s 6–5 win over the Rays Friday night. The plan had been to bring in Ziegler in a setup role as a replacement for another injured Boston reliever, off-season acquisition Carson Smith, who had Tommy John surgery in late May. Kimbrel’s injury may have expedited the consummation of those discussions, but Ziegler was never intended as a replacement for Kimbrel.

As it turns out, Ziegler, who has 81 career saves and converted 48 of 51 save chances for Arizona between taking over the closer role for the Diamondbacks in mid-May of last year and Saturday morning’s trade, still may not replace Kimbrel directly. Boston’s initial plan appears to be to split closing duties between the 36-year-old Ziegler and 41-year-old Koji Uehara, the latter of whom preceded Kimbrel as Boston’s closer and has converted all three of his final-inning save chances this season, two of them coming in the last two weeks. With Ziegler not yet available to Boston, Uehara converted yet another save on Saturday in a 4–1 win over the Rays.

Kimbrel’s injury has changed the narrative on Ziegler’s acquisition, but it would have been an important one for the Red Sox even if Kimbrel had stayed healthy. New general manager Dave Dombrowski invested heavily in the Red Sox bullpen this off-season. In mid-November, he sent an impressive package of prospects to the Padres for Kimbrel, who had $25 million remaining on his contract for this season and next. He also acquired the 26-year-old Smith from the Mariners in a four-player deal less than a month later. Kimbrel is widely regarded as one of the best closers in baseball, and Smith had a tremendous rookie season for Seattle last year, striking out 92 in 70 innings with a 2.31 ERA and a 4.18 strikeout-to-walk ratio.

However, Smith managed to throw just 2 2/3 innings for Boston before succumbing to Tommy John surgery. Kimbrel has thus far posted career-worsts in ERA (3.55), ERA+ (129) and FIP (2.87), and his highest WHIP (1.09), walk rate (4.1 BB/9), and lowest strikeout-to-walk ratio (3.33) since his 21-game debut in 2010, falling well short of the late-game dominance the Red Sox had anticipated when acquiring him in November. Uehara, meanwhile, has been showing his age with career-high home run and walk rates contributing to a 4.96 ERA, and Junichi Tazawa has failed to step up in Carson’s absence, posting a 3.62 ERA and 3.73 FIP thus far this season.

The result has been a Boston bullpen that has been very ordinary, ranked 15th in the majors with a 3.92 ERA. With the rotation also struggling, save for 31-year-old first-time All-Star Steven Wright, the Red Sox’ pitching staff has been a significant drag on the team’s major league-best offense. Boston has scored 5.7 runs per game this season, nearly a half-run per game more than the next best offense in baseball (the Cubs), but has allowed 5.0 runs per game, fewer than only the miserable Twins in the American League and sixth-most in the majors. Had the pitching staff performed up to expectations, the Red Sox would likely be running away with the American League East right now. Instead, they entered Saturday’s action in third place, two games behind the division-leading Orioles, and just one game ahead of the Astros in the AL’s second wild-card spot.

The rotation is the larger concern. Boston’s starters have compiled a 4.84 ERA this season, which ranks 23rd in the majors. You can be sure that Dombrowski will be pursuing starting pitching reinforcements over the next three weeks, and he’s very likely to land at least one given his track record. Ziegler is a nice start for the bullpen, however. A soft-tossing submariner who hasn’t thrown an 89 mph pitch since 2013, averaging 85 mph with his sinker and in the mid 70s with his changeup and slider, Ziegler gives opposing batters an unfamiliar and uncomfortable look and generates a ton of ground balls, which produce rally-killing double plays at roughly twice the league-average rate.

That ground-ball tendency also makes Ziegler an extremely difficult pitcher to take deep. He has allowed just one home run in 38 1/3 innings this season, didn’t allow any in 58 1/3 innings in 2011 and has never allowed more than five in a single season. Zielger doesn’t strike many batters out, but he has nonetheless posted a 2.49 ERA (164 ERA+) over eight-plus major league seasons split between both leagues. With a solid defensive infield behind him, which the Red Sox have, he should be able to continue to succeed in any ballpark.

As for the two players the Red Sox traded to acquire him, neither are elite prospects. It is important here not to confuse Luis Alejandro Basabe with his twin brother, Luis Alexander Basabe. Both are 19-year-old switch hitters from Venezuela. However, Luis Alexander is an outfielder who ranked among the Red Sox’s 10 best prospects this off-season. Luis Alejandro, the player heading to Arizona, is a switch-hitting middle infielder and the lesser of the two players. Jose Almonte, meanwhile, is a 20-year-old right-handed starting pitcher out of the Dominican Republic who has had middling results in the Sally League thus far this year (3.91 ERA, 1.19 WHIP, 7.6 K/9). Either youngster could take a step forward in the Diamondbacks system, but it wouldn’t be surprising if neither proves to be a player of any significance.